Beautify the 3D Brain-Activity Viewer

Issue1:
Currently the Info-texts (especially "timeline" in the 3D Viewer flickers a lot. Also it seems, that it computes down to a so small part of a millisecond, that it cannot be for real. Suggestion: round up that number to 3 digits after the decimal dot and if necessary fill it up with zeros, in case it is shorter. Thus it also has a fixed length and there should be no more flickering.

Issue2:
Also it would be nice, if the visualization-speed could be set. May it be on the timestep, or the FPS. Keep in mind, that still there needs to be a maximum fps, to capture mouse-events still and not have to much dead-times for UI-responsiveness